Tsuge et al.
Int Chin J Dent 2008; 8: 49-52.
Radiopacity of anterior and posterior restorative composites
Takuma Tsuge, DDS,a Shoji Kawashima, DDS, PhD,b Kazuya Honda, DDS, PhD,b
Hiroyasu Koizumi, DDS, PhD,c Hideo Matsumura, DDS, PhD,c and Noriko Hisamatsu,
DDS, PhDd
a
b
Nihon University Graduate School of Dentistry, Department of Oral and Maxillofacial Radiology, and
Division of Advanced Dental Treatment, Dental Research Center, Nihon University School of Dentistry,
c
Department of Fixed Prosthodontics, and Division of Advanced Dental Treatment, Dental Research
d
Center, Nihon University School of Dentistry, Tokyo, Japan, and Nagasaki University Hospital of
Medicine and Dentistry, Nagasaki, Japan
Purpose: The purpose of this study was to evaluate the difference in radiopacity of anterior and posterior
composites.
Materials and Methods: Four composites designed for anterior (Litefil II A and Solare A) or posterior
restorations (Litefil II P and Solare P) were evaluated. Two self-polymerizing acrylic resins (Unifast III and
Provinice) were used as controls. Radiographs of the specimens were taken together with tooth slices and
aluminum step wedges. The density of the specimens was determined with a transmission densitometer and was
expressed in terms of the equivalent thickness of aluminum per 2.0 mm unit thickness of the specimen (mm
Al/2.0 mm specimen).
Results The radiopacity values of composites ranged from 1.5 to 3.7, whereas the two acrylic resins were
radiolucent (less than 0.5).
Conclusion: The radiopacity of composite restorative materials varies considerably, and care must be taken in
the selection of materials. (Int Chin J Dent 2008; 8: 49-52.)
Key Words: aluminum, composite, densitometer, radiopacity.
Introduction
Dental composites are used as restorations, luting agents, base, core foundation, and in many other
applications. Radiopacity is one of the prerequisites for dental materials, especially for composite restorations.
Advantages of radiopaque over radiolucent materials include easy detection of secondary dental caries as well as
observation of the radiographic interface between the materials and tooth structure.
A number of studies have evaluated the radiopacity of dental composites.1-8 Abou-Tabl et al.1 used an
aluminum step wedge as a radiographic reference for evaluating the radiopacity of dental materials. Most
investigators determined the radiopacity of composite on the basis of ISO 4049 standard.9 According to the ISO
4049 guidelines, the radiopacity of a radiopaque material should be equal to or greater than that of the same
thickness of aluminum.
An increasing number of posterior and anterior composite restorative materials have recently been introduced
with improved bonding and handling characteristics. However, only limited information is available about the
radiographic properties of currently available composites. This study determined the radiopacity values of
anterior and posterior composites, and compared these values with those of unfilled acrylic resins.
Materials and Methods
Four restorative composites and two acrylic resins were assessed.
Characteristics of the materials are
summarized in Table 1. Step wedges made of 99.99% aluminum (2.0-20.0 mm in thickness, Seico Inc.,
Hiroshima, Japan) and extracted human molars were employed. This project was approved by the Ethical
Committee of the Nihon University School of Dentistry (2007-5).
Composite paste was poured into acrylic molds (10.0 mm in diameter and 2.3 mm in height) and light-cured
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Int Chin J Dent 2008; 8: 49-52.
between two glass plates at 25˚C.
Monomer liquid and powder of the MMA resins were mixed and
self-polymerized according to the manufacturers' instructions, and 2.3-mm-thick specimens were prepared.
After 24 hours, the specimens were ground with #600 silicon-carbide paper to obtain a thickness of 2.0 mm.
Extracted human molar teeth were sectioned mesiodistally with a rotary cutting machine, wet-polished, and
2.0-mm-thick specimens were prepared.
Table 1.
Materials assessed.
Materials
Manufacturer
Lot
Composition
Direct composite
Solare A
Solare P
GC Corp., Tokyo, Japan
GC Corp.
0610131
0609152
UDMA, SiO2
UDMA, fluoro-alumino silicate, SiO2
Litefil II A
Litefil II P
Shofu Inc., Kyoto, Japan
Shofu Inc.
100640
110658
UDMA, TEGDMA, alumino silicate, fused silica
UDMA, TEGDMA, alumino silicate, fused silica
0605291
0605292
Powder:
Liquid:
PMMA
MMA
060650
100609
Powder:
Liquid:
MMA-EMA copolymer
MMA
Self-polymerizing acrylic resin
Unifast III
GC Corp.
Provinice
Shofu Inc.
UDMA, Urethane dimethacrylate; TEGDMA, Triethyleneglycol dimethacrylate;
PMMA, Poly(methyl methacrylate); MMA, Methyl methacrylate; EMA, Ethyl methacrylate
Each specimen was placed together with tooth slices and aluminum step wedges on a radiographic film
(Ultra-Speed Dental Film DF-50 Occlusal, Eastman Kodak Co., Rochester, NY, USA). Radiographs were taken
with a dental X-ray apparatus (DFW-20, Asahi Roentgen Ind., Kyoto, Japan) for 0.6 s at 60 kVp, 15 mA with a
target-film distance of 35 cm. The total filtration on the X-ray beam was 2 mm aluminum. The films were
processed in an automatic developing machine (Dent-X 9000, AFP Imaging Co., Elmsford, NY, USA) at 27˚C
for 6 minutes. The radiographic density of the films was measured with a transmission densitometer (PDA-15,
Konika-Minolta Inc., Tokyo, Japan). The radiopacity values of the specimens were expressed in terms of the
equivalent thickness of aluminum per 2.0 mm unit thickness of material. For each condition, the mean value and
standard deviation of 10 replications were calculated. The radiopacity values of each group were compared by
Mann-Whitney U test with the value for statistical significance set at the P=0.01 level (SPSS software, Version
14.0.J for Windows, SPSS Japan Inc., Tokyo, Japan).
Results
The radiopacity values of the 2.0-mm-thick composite specimens are presented in Table 2.
A typical
radiograph of the specimens taken together with tooth slices and aluminum step wedges is shown in Fig. 1.
Statistical analysis results are also summarized in Table 2. The radiopacity values of composites were 1.5 for
Solare A, 3.7 for Solare P, 1.8 for Litefil II A, and 2.2 for Litefil II P. The two acrylic resins were radiolucent,
and the radiopacity values were less than 0.5. For each composite, the posterior material was more radiopaque
than the anterior material (P<0.001). The radiopacity values of human enamel and dentin were approximately
4.3 and 2.3 mm Al/2.0 mm specimen, respectively. Radiopacity values of the Litefil II composites were smaller
than that of dentin.
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Table 2.
Int Chin J Dent 2008; 8: 49-52.
Radiopacity values of direct composites (mm Al/2 mm specimen)
Material
Median Mean
SD
Material
Median Mean
SD
Z-value
P-value
Solare A
Litefil II A
1.5
1.8
0.1
0.1
Solare P
Litefil II P
3.8
2.2
0.2
0.1
-3.883
-3.914
P<0.001
P<0.001
1.5
1.8
Z-value=-3.933 P-value <0.001
3.7
2.2
Z-value=-3.865 P-value <0.001
Fig. 1.
A radiograph of Solare A, Solare P
(top), Litefil II A, Litefil II P (middle),
Unifast III, and Provinice (bottom).
Two acrylic resins were
radiolucent, and were difficult to
detect on the radiograph.
Discussion
Polymeric dental materials can be made radiopaque by incorporation of radiopaque elements into either the
filler particles or monomer liquids.
Zirconia, silica-zirconia, barium glass, barium sulfate and ytterbium
trifluoride are useful for enhancing the radiopacity of dental composites. They are usually added to inorganic
fillers before preparation of splintered filler particles. The results of the current study revealed that radiopacity
values of the Litefil II composites were not particularly high. This is probably derived from the fact that the
amount of radiopaque elements added to the composite was not sufficient. The radiopacity values of the Solare
composites also were not high, and the values were smaller than that of enamel. As revealed in the current
investigation, the four composite materials showed radiopacity values below that of enamel, and two anterior
composites showed radiopacity values below that of dentin. The values may be sufficient to allow detection in
some cavity preparations. However, the use of radiolucent materials may lead to an incorrect diagnosis. A
radiopacity value equal to or slightly greater than that of enamel is therefore desirable for restorative composites.
Acknowledgments
This work was supported in part by Sato Fund, Nihon University School of Dentistry (2008), Grant from Dental Research
Center (A and B), Nihon University School of Dentistry (2008), and Special Research Grant for the Development of
Distinctive Education from the Promotion and Mutual Aid Corporation for Private Schools of Japan (2008).
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Correspondence to:
Dr. Hiroyasu Koizumi
Department of Fixed Prosthodontics, Nihon University School of Dentistry
1-8-13, Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
Fax: +81-3-3219-8351 E-mail: [email protected]
Received September 16, 2008. Accepted November 11, 2008.
Copyright ©2008 by the International Chinese Journal of Dentistry.
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